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During a routine surgical procedure, a patient developed premature ventricular contractions. The anesthesiologist told the circulating nurse to administer a bolus of 100 mg of lidocaine (lignocaine) through an injection port on the patient's I.V. line. He removed the prefilled syringe from its box and handed it to her. The nurse injected the drug into the infusing I.V. line, and injected a second dose a few minutes later at the anesthesiologist's request.
Soon after the two doses had been injected, another operating room (OR) nurse picked up the empty syringes and saw they were labeled: "lidocaine, 1 gram. CAUTION: MUST BE DILUTED." The patient had received 2 grams of lidocaine rather than the 200 mg intended.
After surgery, the patient was closely monitored, and he survived the accidental overdose. But he was lucky; similar mix-ups between 100-mg and I-gram lidocaine syringes have caused death.
Why did this potentially fatal medication error occur? Two factors contributed to it.
First is the confusion inherent in having two types of lidocaine prefilled syringes available. One type, containing either 50 or 100 mg, is intended for I.V. bolus injection. The second type (the one accidentally injected in this incident) contains either 1 or 2 grams of the drug. These syringes are intended for preparing large-volume dilutions of lidocaine for continuous infusion.
The 1- and 2-gram syringes, manufactured by several companies, contain concentrated lidocaine. This type of syringe has a very short needle, which allows it to be used as a universal additive syringe. In other words, you can use it to add the drug to a glass I.V. bottle, through the rubber stopper, or to an I.V. bag, through its injection port.
The universal additive syringes look quite different from syringes meant for bolus injections-a bulbous cap covers most of the needle. Also, they're clearly marked CAUTION: MUST BE DILUTED. But the needle does stick out far enough from the cap to fit into an injection port or intermittent infusion (INT) device.
The second contributing factor is that some hospitals routinely stock both types of syringes in the OR on crash carts and on nursing units. This practice can lead to confusion in an emergency. True-the boxes in which they're packaged have different colors. But in this incident, a doctor removed a syringe from its
box and handed it to a nurse to administer. The nurse didn't see the box. And hurrying to administer the drug, she didn't take time to read the syringe's label, assuming that the doctor had checked it.
Avoid stocking concentrated lidocaine syringes at all. Vials of concentrate with transfer sets are available; and recently, three manufacturers of large volume parenterals have introduced premixed solutions of lidocaine in glass and plastic containers-ready to infuse. Consider discussing these alternatives with your hospital pharmacist